The invention relates to systems for processing liquid waste, particularly septic or leaching system waste. More particularly the invention relates to methods, apparatuses and systems for removing nitrogen-containing and other compounds such as phosphorus and suspended solids from waste water such as that in septic systems. The system includes, in part, a process of alternating aerobic, anaerobic, and aerobic conditions, with the addition of carbon, waste processing treatments and a fluid retaining means, eliminates nitrogen compounds such as ammonia, nitrates and nitrites, as well as other materials, from septic system waste as it is processed. Thus, the present invention effectively and efficiently processes contaminated waste water.